using System;
using System.Collections.Generic;
using System.Text;
using System.IO;
using System.Security.Cryptography;

namespace Protocolo
{
    /// <summary>
    /// Clase para Encriptar y Desencriptar password.
    /// Tomada de Internet.
    /// </summary>
    public class Desencriptar
    {
        // Encrypt a byte array into a byte array using a key and an IV 
        public static byte[] Encrypt(byte[] clearData, byte[] Key, byte[] IV)
        {
            // Create a MemoryStream that is going to accept the encrypted bytes 
            MemoryStream ms = new MemoryStream();

            // Create a symmetric algorithm. 
            // We are going to use Rijndael because it is strong and available on all platforms. 
            // You can use other algorithms, to do so substitute the next line with something like 
            //                      TripleDES alg = TripleDES.Create(); 

            Rijndael alg = Rijndael.Create();

            // Now set the key and the IV. 
            // We need the IV (Initialization Vector) because the algorithm is operating in its default 
            // mode called CBC (Cipher Block Chaining). The IV is XORed with the first block (8 byte) 
            // of the data before it is encrypted, and then each encrypted block is XORed with the 
            // following block of plaintext. This is done to make encryption more secure. 
            // There is also a mode called ECB which does not need an IV, but it is much less secure. 

            alg.Key = Key;
            alg.IV = IV;

            // Create a CryptoStream through which we are going to be pumping our data. 
            // CryptoStreamMode.Write means that we are going to be writing data to the stream 
            // and the output will be written in the MemoryStream we have provided. 

            CryptoStream cs = new CryptoStream(ms, alg.CreateEncryptor(), CryptoStreamMode.Write);

            // Write the data and make it do the encryption 
            cs.Write(clearData, 0, clearData.Length);

            // Close the crypto stream (or do FlushFinalBlock). 
            // This will tell it that we have done our encryption and there is no more data coming in, 
            // and it is now a good time to apply the padding and finalize the encryption process. 

            cs.Close();

            // Now get the encrypted data from the MemoryStream. 
            // Some people make a mistake of using GetBuffer() here, which is not the right way. 

            byte[] encryptedData = ms.ToArray();

            return encryptedData;

        }


        // Encrypt a string into a string using a password 
        //    Uses Encrypt(byte[], byte[], byte[]) 
        public static string Encrypt(string clearText, string Password)
        {
            // First we need to turn the input string into a byte array. 
            byte[] clearBytes = Encoding.Unicode.GetBytes(clearText);

            // Then, we need to turn the password into Key and IV 
            // We are using salt to make it harder to guess our key using a dictionary attack - 
            // trying to guess a password by enumerating all possible words. 
            PasswordDeriveBytes pdb = new PasswordDeriveBytes(Password,

                        new byte[] { 0x49, 0x76, 0x61, 0x6e, 0x20, 0x4d, 0x65, 0x64, 0x76, 0x65, 0x64, 0x65, 0x76 });

            // Now get the key/IV and do the encryption using the function that accepts byte arrays. 
            // Using PasswordDeriveBytes object we are first getting 32 bytes for the Key 
            // (the default Rijndael key length is 256bit = 32bytes) and then 16 bytes for the IV. 
            // IV should always be the block size, which is by default 16 bytes (128 bit) for Rijndael. 
            // If you are using DES/TripleDES/RC2 the block size is 8 bytes and so should be the IV size. 
            // You can also read KeySize/BlockSize properties off the algorithm to find out the sizes. 
#pragma warning disable 618,612
            byte[] encryptedData = Encrypt(clearBytes, pdb.GetBytes(32), pdb.GetBytes(16));
#pragma warning restore 618,612

            // Now we need to turn the resulting byte array into a string. 
            // A common mistake would be to use an Encoding class for that. It does not work 
            // because not all byte values can be represented by characters. 
            // We are going to be using Base64 encoding that is designed exactly for what we are 
            // trying to do. 

            return Convert.ToBase64String(encryptedData);
        }


        // Decrypt a byte array into a byte array using a key and an IV 
        public static byte[] Decrypt(byte[] cipherData, byte[] Key, byte[] IV)
        {
            // Create a MemoryStream that is going to accept the decrypted bytes 
            MemoryStream ms = new MemoryStream();

            // Create a symmetric algorithm. 
            // We are going to use Rijndael because it is strong and available on all platforms. 
            // You can use other algorithms, to do so substitute the next line with something like 
            //                      TripleDES alg = TripleDES.Create(); 
            Rijndael alg = Rijndael.Create();

            // Now set the key and the IV. 
            // We need the IV (Initialization Vector) because the algorithm is operating in its default 
            // mode called CBC (Cipher Block Chaining). The IV is XORed with the first block (8 byte) 
            // of the data after it is decrypted, and then each decrypted block is XORed with the previous 
            // cipher block. This is done to make encryption more secure. 
            // There is also a mode called ECB which does not need an IV, but it is much less secure. 

            alg.Key = Key;
            alg.IV = IV;

            // Create a CryptoStream through which we are going to be pumping our data. 
            // CryptoStreamMode.Write means that we are going to be writing data to the stream 
            // and the output will be written in the MemoryStream we have provided. 
            CryptoStream cs = new CryptoStream(ms, alg.CreateDecryptor(), CryptoStreamMode.Write);

            // Write the data and make it do the decryption 
            cs.Write(cipherData, 0, cipherData.Length);

            // Close the crypto stream (or do FlushFinalBlock). 
            // This will tell it that we have done our decryption and there is no more data coming in, 
            // and it is now a good time to remove the padding and finalize the decryption process. 
            cs.Close();

            // Now get the decrypted data from the MemoryStream. 
            // Some people make a mistake of using GetBuffer() here, which is not the right way. 
            byte[] decryptedData = ms.ToArray();

            return decryptedData;

        }


        // Decrypt a string into a string using a password 
        //    Uses Decrypt(byte[], byte[], byte[]) 
        public static string Decrypt(string cipherText, string Password)
        {
            // First we need to turn the input string into a byte array. 
            // We presume that Base64 encoding was used 
            byte[] cipherBytes = Convert.FromBase64String(cipherText);

            // Then, we need to turn the password into Key and IV 
            // We are using salt to make it harder to guess our key using a dictionary attack - 
            // trying to guess a password by enumerating all possible words. 
            PasswordDeriveBytes pdb = new PasswordDeriveBytes(Password,

                        new byte[] { 0x49, 0x76, 0x61, 0x6e, 0x20, 0x4d, 0x65, 0x64, 0x76, 0x65, 0x64, 0x65, 0x76 });

            // Now get the key/IV and do the decryption using the function that accepts byte arrays. 
            // Using PasswordDeriveBytes object we are first getting 32 bytes for the Key 
            // (the default Rijndael key length is 256bit = 32bytes) and then 16 bytes for the IV. 
            // IV should always be the block size, which is by default 16 bytes (128 bit) for Rijndael. 
            // If you are using DES/TripleDES/RC2 the block size is 8 bytes and so should be the IV size. 
            // You can also read KeySize/BlockSize properties off the algorithm to find out the sizes. 
            #pragma warning disable 618,612
            byte[] decryptedData = Decrypt(cipherBytes, pdb.GetBytes(32), pdb.GetBytes(16));
            #pragma warning restore 618,612

            // Now we need to turn the resulting byte array into a string. 
            // A common mistake would be to use an Encoding class for that. It does not work 
            // because not all byte values can be represented by characters. 
            // We are going to be using Base64 encoding that is designed exactly for what we are 
            // trying to do. 

            return Encoding.Unicode.GetString(decryptedData);
        }

    }
}
